COKDYLARTHRA. 411 



Both of the specimens of this species were found in the lowest Puerco 

 beds of New Mexico by Mr. D. Baldwin. 



Anisonchus gillianus Cope. 



Proceed. Amer. Pliilos. Soc, 1882, p. 467; Saploconusgillianus Cope, American Naturalist, 1882, p. 686 



Plate XXV/; figs. 10-11. 



This animal is the smallest of the family of the Periptychidce which is 

 yet known. There are parts of five individuals in my collection which in- 

 clude the dentition of both jaws exclusive of the most anterior teeth. Two 

 of these consist of fragments of the lower jaw only. Two others include 

 parts of both jaws, and one includes only the right maxillary bone with 

 teeth. 



The typical specimen displays the second and third superior premolars 

 and first two true molars, with the second and fourth inferior premolars, 

 and last two true molars. The fourth superior premolar is lost from this 

 specimen, but I exposed it in a second one, after removing the decidious 

 tooth which preceded it. The second superior premolar has but two roots, 

 the anterior and interior being fused. The section of the base of the crown 

 is a spherical triangle with the apex anterior. It has a low cingulum except 

 at the external base. The apex of the crown is compressed so as be a fore 

 and aft edge. The third superior premolar is similar as to its external cusp, 

 which is larger than that of the second. The internal cusp is three-quarters 

 the height of the external, and the apex is compressed so as to be antero- 

 posterior, The diameter of its base is only lialf that of the external cusp. 

 There is a cingulum which is weak externally and wanting internally. The 

 second true molar has greater transverse extent than the first or fourth. 

 The external cusps are slightly convex externally. The V is not produced 

 inwards, while the posterior internal cusp does stand well inwards, its base 

 being especially prominent. It is posterior to the middle line, though entirely 

 interior to the apex of the V. Besides the posterior cingulum, the strong 

 anterior cingulum reaches nearly to its anterior base. The third true 

 molar is equal to the first. 



In the inferior series the second premolar has a small anterior basal 



tubercle, a robust acute median cusp, and a small heel whose outline is a 



' circular ridge. The fourth premolar is like the second, but all the parts 



